Examples of optical discs serving as optical information recording media include compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs (BDs) (registered trademark), and the like. The recording density of these optical discs has been gradually becoming higher. In recent years, an optical information recording medium that can record a large amount of information has been required as the volume of information increases.
Volumetric recording in which information is recorded in the depth direction of a recording layer of an optical information recording medium is used as a method for recording a large amount of information on an optical information recording medium. Representative volumetric recording formats are a multilayer optical disc, volumetric recording that uses two-photon absorption, volumetric hologram recording, and the like (Japanese Unexamined Patent Application Publication No. 2005-100606).
However, for example, in the case of a multilayer optical disc, although it is important that recording layers composed of a resin into which signal pits are transferred from a metal stamper and a reflective film be precisely stacked, these steps are extremely complicated and a significant cost increase cannot be avoided due to a low yield.
Furthermore, in the case of volumetric recording that uses two-photon absorption, since the development of a highly stable recording medium and a high-power laser such as a femto-second laser are required, the cost of the entire system increases.
Moreover, in the case of volumetric hologram recording, a decrease in an S/N ratio with increasing medium noise caused by conducting multiplex recording, the difficult handling of a photopolymer medium, the necessity of a spatial modulator with many pixels and an image sensor, and the like increase the cost of the entire system.
As described above, all of these volumetric recording methods are disadvantageous for realizing practical use because a system for manufacturing an optical information recording medium is complicated and the cost of the entire system increases.
Accordingly, an object of the present invention is to manufacture an optical information recording medium having a recording layer that can record a large amount of information, using a simple system.